US5773813A - Angular position finding system for an observation instrument - Google Patents

Angular position finding system for an observation instrument Download PDF

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Publication number
US5773813A
US5773813A US08/652,550 US65255096A US5773813A US 5773813 A US5773813 A US 5773813A US 65255096 A US65255096 A US 65255096A US 5773813 A US5773813 A US 5773813A
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United States
Prior art keywords
light
mirror
instrument
angular position
finding system
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Expired - Fee Related
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US08/652,550
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English (en)
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Paul Duchon
Georges Otrio
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Centre National dEtudes Spatiales CNES
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Centre National dEtudes Spatiales CNES
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Assigned to CENTRE NATIONAL D'ETUDES SPATIALES reassignment CENTRE NATIONAL D'ETUDES SPATIALES ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DUCHON, PAUL, OTRIO, GEORGES
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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/16—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using electromagnetic waves other than radio waves
    • G01S5/163—Determination of attitude
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
    • G01C11/00—Photogrammetry or videogrammetry, e.g. stereogrammetry; Photographic surveying
    • G01C11/02—Picture taking arrangements specially adapted for photogrammetry or photographic surveying, e.g. controlling overlapping of pictures
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S17/00—Systems using the reflection or reradiation of electromagnetic waves other than radio waves, e.g. lidar systems
    • G01S17/87—Combinations of systems using electromagnetic waves other than radio waves
    • G01S17/875—Combinations of systems using electromagnetic waves other than radio waves for determining attitude
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S3/00—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received
    • G01S3/78—Direction-finders for determining the direction from which infrasonic, sonic, ultrasonic, or electromagnetic waves, or particle emission, not having a directional significance, are being received using electromagnetic waves other than radio waves
    • G01S3/782—Systems for determining direction or deviation from predetermined direction
    • G01S3/785—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system
    • G01S3/786—Systems for determining direction or deviation from predetermined direction using adjustment of orientation of directivity characteristics of a detector or detector system to give a desired condition of signal derived from that detector or detector system the desired condition being maintained automatically
    • G01S3/7867—Star trackers
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B23/00—Telescopes, e.g. binoculars; Periscopes; Instruments for viewing the inside of hollow bodies; Viewfinders; Optical aiming or sighting devices

Definitions

  • the invention concerns an angular position finding system for an observation instrument, and in particular may be incorporated into an artificial satellite, a space vehicle or a space station.
  • observation instruments may need to take pictures that have to be located with very high precision.
  • the position and orientation of the instrument on the element that acts as a support are frequently not known sufficiently precisely.
  • sighting change systems in other words instruments that modify the orientation of the line of sight of the observation instrument.
  • These instruments are required whenever it is disadvantageous or impossible to rotate the entire instrument support machinery, or when it is impossible to wait until the instrument has reached its required orientation by natural means, which occurs periodically on unstabilized satellites.
  • Sighting change equipment acts on the observation instrument either by displacing the instrument itself, or by moving its line of sight (this solution is frequently used on satellites).
  • the instrument then consists of a rotating mirror.
  • Any sighting change equipment introduces an additional uncertainty in the orientation of the line of sight, due to uncertainty about its mounting position or about the precision of its control, which for example can produce an uncertainty in the orientation of the sighting change mirrors.
  • expansions caused by temperature changes can deform instrument support structures, particularly on satellites exposed to very large temperature differences between the surface illuminated by the sun and the surface in the shade.
  • This invention is designed specifically to eliminate this problem of directional inaccuracy by means of a system which, in its most general form, includes a first light pattern source rigidly attached to the instrument close to the focal plane of the instrument and consisting of at least two dots; a light sensor fixed at a know direction on the space vessel to which the instrument and the system are fixed; and a reflection mirror positioned to reflect light from the source to the sensor the mirror being rigidly attached either to the sensor or to the sighting change mirror (if there is one).
  • the position of the image of the light pattern on the sensor expresses the instrument orientation. If the system does not include any other particular elements, the orientation of the reflecting mirror (which must not be confused with the sighting change mirror) must be accurately known, which for example is possible if it is mounted carefully on a support rigidly attached to the sensor.
  • the light sensor may consist of a star sensor which is fairly frequently used in satellites. It then provides its own directional reference by detecting the image of reference stars at the same time as it detects the image of the light pattern, and compares the position of the two images on its screen.
  • the directional reference may also be completed by a gyroscopic assembly, which is then rigidly attached to the light sensor.
  • the reflecting mirror may form an angle and include two plane facets separated by an edge, with one facet reflecting light from the first source and the other facet reflecting light from the second source, so that the position of the sensor with respect to the instrument is unimportant.
  • the reflecting mirror may include a facet elongated perpendicularly to the axis of rotation of the sighting change mirror and that reflects the light pattern from the first source to one of the sides of the axis of rotation of the sighting change mirror along which the light sensor lies.
  • the sensor is located at the side of the instrument sighting trajectory and therefore does not intercept it, and the light sensor is useful for a long angular movement of the sighting change mirror.
  • FIG. 1 shows some essential elements of a first embodiment of the system according to the invention
  • FIG. 1a schematically shows the light sensor screen
  • FIG. 1b represents a change to a detail in the first embodiment
  • FIG. 2 shows installation of the light sensor
  • FIG. 2a shows the formation of images on the light sensor screen
  • FIG. 3 represents a reflecting mirror
  • FIGS. 4a and 4b show details of another complete embodiment of the invention, and in particular show reflecting mirrors according to FIG. 3,
  • FIG. 5 shows another way of making the invention, with a different reflecting mirror
  • FIGS. 6 and 7 illustrate a mobile screen used in relation to the invention.
  • FIGS. 1 and 1a The observation instrument 1 is fixed on the satellite and is shown partially, and in particular has an apparent surface 2 which coincides with its focal plane and is fitted with an observation sensor module 3 and four light emitting diodes 4 flush with its surface (two light sources may be sufficient, as we will see later), each emitting a laser light beam that can be recognized by the light sensors.
  • Two of the four diodes 4 are placed at the ends of the sensor module 3, and the other two are placed on its sides at mid-distance from the first two. It is advantageous to only use one emitting laser-diode 4 (shown on FIG. 1b) in front of a divergent beam of optical fibers 41, each of which captures part of its light and leads to the same emission points, at ends 42, such that the effect is the same.
  • An optical system 5 is placed in front of the observation instrument 1. It is symbolized in the form of a focusing lens, but may be of any known type depending on the needs and properties of instrument 1.
  • One of its effects is to defocus the rays output from diodes 4 to spread their light according to rays 8 occupying a front with a wide surface.
  • a sighting change mirror 6 is placed in front of the optical system 5. This mirror rotates about an axis of rotation 7 and its total movement may be, for example, 30°. Light rays originating from the observation point moving along a line of sight L reach the instrument 1 after being reflected by the sighting change mirror 6. Rays 8 are not necessarily reflected on the sighting change mirror 6, since they pass through a hole 44 formed through it, or at the side of it. They are only reflected by a second mirror, called the reflection mirror 9, which is rigidly attached to the sighting change mirror 6 and which is fixed on one side of hole 44.
  • alignment sensor 43 a light sensor
  • optical system 11 capable of converging beams 8 onto a sensitive surface 12 on the alignment sensor 10 formed of a rectangle, in this case a square, of detectors 13 (FIG. 1a).
  • a computer (not shown) built into the alignment sensor 43 breaks down the image recorded globally by detectors 13 to deduce the global direction of the satellite, to which the alignment sensor 43 is assumed to be fixed at a perfectly known direction. It is fixed to a plate 45 connected to the satellite, to which a star sensor (stellar sensor) 46 and a gyroscope 47 are also attached, and which output a direction reference in a fixed coordinate system.
  • Defocusing light from diodes 4 means that the reflecting mirror 9 remains within the front of rays 8 for all rotations of the sighting change mirror 6.
  • FIGS. 2 and 2a provide information about making a sophisticated alignment sensor 10 which can simultaneously act as a star sensor, but some of this information may also be applicable to the previous alignment sensor 43.
  • a screen 14 is placed in front of the optics 11 of the alignment sensor 10 to blank off parasite light.
  • a half-mirror 15 is recessed in screen 14 which consists of two horns, one of which 16 supporting half-mirror 15 lies along an extension of the optical axis of the alignment sensor 10, and the other 17 is connected to the first and is located in front of the half-mirror 15.
  • the half-mirror 15 is used so that the alignment sensor 10 collects light forming images from two different directions.
  • the half-mirror 15 acts as a filter for each measurement direction, and makes it possible to distinguish between images of stars and diodes 4 on the sensitive surface 12 based on their colors, and with no possibility of error.
  • FIGS. 3, 4a and 4b illustrates the specific embodiment of some of the above reasoning.
  • the description of FIG. 1 remains applicable concerning the observation instrument 1, the sighting change mirror 6 and connected parts. But the system as described so far is not necessarily sufficient since rotations of the reflecting mirror 9 about an axis perpendicular to its reflection plane are not detected by alignment sensor 10.
  • the alignment sensor 10 is fitted with two additional light emitting diodes 19 (FIG. 2a) at the edges of the square of detectors 13, and the rays 20 of which are directed towards the reflecting mirror 9 and are then reflected by it and return almost to their starting point, on the square of detectors 13.
  • the image of this light pattern supplies the orientation of reflecting mirror 9 by its position on the sensor square 13.
  • the light pattern P8 moves along a line L8 depending on the rotation of the sighting change mirror 6, the line possibly being a diagonal of the square of detectors 13, and points P20 are away from it.
  • the reflecting mirror 56 for this embodiment is complex and is formed of three different facets, one of which denoted 21 is an oblique sheet at 45° and is designed to reflect rays 8 at a right angle.
  • the other two facets 22 and 23 are located approximately perpendicularly to the axis of rotation 7 (at an angle which can however vary between about 60° and 120° in practice), at the ends of the previous facet 21, and which return rays 20 from diodes 19 to the star sensors and alignment sensors 10a or 10b, of which there are two in this embodiment for reasons which will be explained.
  • FIGS. 4a and 4b Another method of making large movements for the sighting change mirror 6 compatible with the invention consists of duplicating the position finding system: this solution is shown here, and is clearly visible on FIGS. 4a and 4b, on which there are two different reflecting mirrors 56a and 56b which reflect rays 8 in lateral and opposite directions parallel to the axis of rotation 7, to two alignment sensors 10a and 10b approximately facing each other.
  • reflecting mirrors 56a and 56b are independent of the sighting change mirror 6 and are related to the satellite body through support surfaces 57a and 57b; they are parallel and slightly offset in front of the sighting change mirror 6, in the transverse direction so that the rays 20 that they return to alignment sensors 10a and 10b are not intercepted by the other reflecting mirror 56, and in the longitudinal direction to cover the entire angular movement of the sighting change mirror 6.
  • a portion of the rays 8 occupying a beam 8i is reflected on the sighting change mirror 6 to form a light spot 58i, and is reflected on the reflecting mirror 56b to form a light spot 59i close to support surface 57b; the corresponding rays 8 are returned to the alignment sensor 10b to form the diode image 4.
  • the sighting change mirror 6 has a total angular movement of 30°, such that the line of sight L can be moved by 60°, which is close to the maximum of known satellite embodiments.
  • the sensitive area 12 will be selected to be a square of detectors 13 with 1024 image points along each side for an angle of vision of 26°, which means that the angle of vision is ⁇ 2.26°, namely about 37° along a diagonal (line L8). Facet 21 is inclined of 45° on the axis of rotation 7, but this is not essential, nor necessarily s the optimum.
  • the sensitive surface 22 detects stars between orders of magnitude of about -2.5 and +4.5, such that it is always possible to locate at least one.
  • light dots P20 and dots in pattern P8 appear in the form of spots which extend over two, three or four image dots due to defocusing, aberration and diffraction.
  • the optical system 11 is not designed to focus rays 8 perfectly, but rather to form small separate light spots, each of which corresponds to the light from one of the diodes 4.
  • the center of gravity method used to estimate the position of the spots, used on stellar sensors, is then used for each light spot (originating from diodes 4, 19 and detected stars) to calculate the center of the spot, equivalent to the projection of the associated light source assumed to be a point.
  • the reflecting mirror could be smaller if the instrument is used without the sighting change mirror. It is referenced by 25 in an embodiment of this type drawn in FIG. 5, and consists of two facets 26 and 27 limited by an edge 28, the first of which is designed to reflect rays 8 from diodes 4 on instrument 1 to alignment sensor 10 (with low field of vision unlike the corresponding solution with the sighting change mirror), and the second part of which is used to reflect rays 20 from diodes 19 in the alignment sensor 10.
  • Reference 29 indicates to a single screen that limits the field of vision of the instrument and the parasite radiation that it receives. Rays 8 reflected by mirror 25, and rays 20 pass through a hole 55 which is formed in it.
  • the direction of instrument 1 is estimated by measuring the positions of the spots corresponding to the different diodes 4 and 19 on the sensitive surface of the alignment sensor 10, and correlating them to the direction of the alignment sensor 10, deduced from a stellar reference or another reference, or known in advance.
  • diodes 19 and facet 27 may be omitted if the orientation of the reflection mirror 25 is well known.
  • FIG. 6 illustrates it in a construction using two of these screens 30a and 30b, which consist of a membrane in which a hole 31 has been cut out.
  • the shape of the holes 31, elliptical in this case, and their surface area are adapted to the width of the field of vision of instrument 1. Since the screens are placed in front of the sighting change mirror 6, they should be moved to correspond with it, and keep holes 31 on the sighting field. Consequently, the membrane of each screen 30 extends between two rollers 32 and 33, around which its ends are wound and at least one of which is driven by a motor 34 and the other may be driven in a similar way by another motor to form a redundant system.
  • Rollers 32 and 33 are connected to spindles 35 rotating in a support frame 36 (which also supports alignment sensor 10 and the hinge pin 7 of the sighting change mirror 6), and a spring 37 applies a force along one of the spindles 35 in a direction of rotation which always tends to tension screen 30.
  • Spring 37 may be helical or spiral and its stiffness is sufficiently small so that it exerts a force which does not vary much with rotations of the roller 33 on which it acts. If a motor 34 is used on each roller 32 and 33, a spring 37 may also be fitted on each of rollers 32 and 33 in order to control one of motors 34 at a time, and to apply tension along axis 35 which is not controlled.
  • Cables 38 are tensioned between rollers 32 and 33 parallel to screen 30, and are preferably distributed on both sides of the screen. Their ends are actually wound around pulleys 39, some of which (one per cable 38) are mounted rigidly on axes 35, and the others are mounted slidingly along axes 35 and are acted upon by springs not shown, similar to springs 37, in order to tension cables 38 at the same time as screen 30.
  • cables 38 The purpose of cables 38 is to simultaneously drive the two rollers 33 with a single motor 34, and incidentally to provide dynamic compensation for movements of screen 30.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Radar, Positioning & Navigation (AREA)
  • General Physics & Mathematics (AREA)
  • Remote Sensing (AREA)
  • Electromagnetism (AREA)
  • Optics & Photonics (AREA)
  • Multimedia (AREA)
  • Astronomy & Astrophysics (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Navigation (AREA)
  • Telescopes (AREA)
  • Length Measuring Devices By Optical Means (AREA)
US08/652,550 1993-12-10 1994-12-09 Angular position finding system for an observation instrument Expired - Fee Related US5773813A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9314872 1993-12-10
FR9314872A FR2713785B1 (fr) 1993-12-10 1993-12-10 Système de repérage d'orientation d'un instrument d'observation.
PCT/FR1994/001441 WO1995016219A1 (fr) 1993-12-10 1994-12-09 Systeme de reperage d'orientation d'un instrument d'observation

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US (1) US5773813A (fr)
EP (1) EP0733226B1 (fr)
JP (1) JPH09509738A (fr)
CA (1) CA2178624A1 (fr)
DE (1) DE69413251T2 (fr)
FR (1) FR2713785B1 (fr)
WO (1) WO1995016219A1 (fr)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2818469A1 (fr) * 2000-12-14 2002-06-21 Cit Alcatel Dispositif de determination de la direction visee par un faisceau emis depuis un satellite en orbite et satellite equipe d'un tel dispositif
US20060103925A1 (en) * 2004-10-07 2006-05-18 Eads Astrium Sas Optical system with variable pointing and method implementing such a system
US20110317153A1 (en) * 2010-06-24 2011-12-29 Apple Inc. Laser peak energy point calibration method and apparatus
US20120113408A1 (en) * 2007-12-18 2012-05-10 Epcos Ag Radiation Sensor for Detecting the Position and Intensity of a Radiation Source
US20190033430A1 (en) * 2017-03-17 2019-01-31 Waymo Llc Variable Beam Spacing, Timing, and Power for Vehicle Sensors

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
AU4197197A (en) * 1996-09-17 1998-04-14 Allied-Signal Inc. Satellite attitude sensor using thermal imaging
DE19927012C1 (de) * 1999-06-07 2001-01-18 Deutsch Zentr Luft & Raumfahrt Kalibrationseinrichtung für die Orientierungsparameter von digitalen optoelektronischen Sensorsystemen in Trägersystemen zur Fernerkundung
CN108426523A (zh) * 2018-03-02 2018-08-21 北京空间技术研制试验中心 一种精度基准转移方法

Citations (3)

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Publication number Priority date Publication date Assignee Title
US4173414A (en) * 1976-10-18 1979-11-06 Societe De Fabrication D'instruments De Mesure (S.F.I.M.) Method and apparatus for correcting the aiming of an optical illuminator on a target
US4349838A (en) * 1980-02-01 1982-09-14 Thomson-Csf Laser target designator system
US4740682A (en) * 1986-07-23 1988-04-26 Michael Frankel Optical tracking, focusing, and information receiving device including a pyramidal light splitter

Family Cites Families (3)

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Publication number Priority date Publication date Assignee Title
US4123164A (en) * 1977-01-03 1978-10-31 The Singer Company Autocollimating assembly for the self-calibration of a stellar navigational system
US4187422A (en) * 1977-12-05 1980-02-05 The Singer Company Internal reference for stellar tracker
US4154532A (en) * 1978-04-20 1979-05-15 The United States Of America As Represented By The Secretary Of The Navy High precision optical alignment system

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4173414A (en) * 1976-10-18 1979-11-06 Societe De Fabrication D'instruments De Mesure (S.F.I.M.) Method and apparatus for correcting the aiming of an optical illuminator on a target
US4349838A (en) * 1980-02-01 1982-09-14 Thomson-Csf Laser target designator system
US4740682A (en) * 1986-07-23 1988-04-26 Michael Frankel Optical tracking, focusing, and information receiving device including a pyramidal light splitter

Cited By (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2818469A1 (fr) * 2000-12-14 2002-06-21 Cit Alcatel Dispositif de determination de la direction visee par un faisceau emis depuis un satellite en orbite et satellite equipe d'un tel dispositif
US20060103925A1 (en) * 2004-10-07 2006-05-18 Eads Astrium Sas Optical system with variable pointing and method implementing such a system
US7385759B2 (en) 2004-10-07 2008-06-10 Eads Astrium Sas Optical system with variable pointing and method implementing such a system
US8705014B2 (en) * 2007-12-18 2014-04-22 Epcos Ag Radiation sensor for detecting the position and intensity of a radiation source
US20120113408A1 (en) * 2007-12-18 2012-05-10 Epcos Ag Radiation Sensor for Detecting the Position and Intensity of a Radiation Source
EP2629112A1 (fr) * 2007-12-18 2013-08-21 Epcos Ag Capteur de rayonnement conçu pour détecter la position et l'intensité d'une source de rayonnement
US20110317153A1 (en) * 2010-06-24 2011-12-29 Apple Inc. Laser peak energy point calibration method and apparatus
US20190033430A1 (en) * 2017-03-17 2019-01-31 Waymo Llc Variable Beam Spacing, Timing, and Power for Vehicle Sensors
US10365351B2 (en) * 2017-03-17 2019-07-30 Waymo Llc Variable beam spacing, timing, and power for vehicle sensors
US10416290B2 (en) * 2017-03-17 2019-09-17 Waymo Llc Variable beam spacing, timing, and power for vehicle sensors
US10634769B2 (en) * 2017-03-17 2020-04-28 Waymo Llc Variable beam spacing, timing, and power for vehicle sensors
US10788571B2 (en) 2017-03-17 2020-09-29 Waymo Llc Variable beam spacing, timing, and power for vehicle sensors
US11333746B2 (en) 2017-03-17 2022-05-17 Waymo Llc Variable beam spacing, timing, and power for vehicle sensors

Also Published As

Publication number Publication date
DE69413251T2 (de) 1999-04-22
FR2713785A1 (fr) 1995-06-16
DE69413251D1 (de) 1998-10-15
CA2178624A1 (fr) 1995-06-15
JPH09509738A (ja) 1997-09-30
WO1995016219A1 (fr) 1995-06-15
FR2713785B1 (fr) 1996-03-01
EP0733226B1 (fr) 1998-09-09
EP0733226A1 (fr) 1996-09-25

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